A typical linear brushless DC (BLDC) motor system is illustrated in FIG. 1. As shown in FIG. 1, the typical BLDC motor system includes a linear BLDC motor 100, a BLDC amplifier 102 and a motor controller 104. The linear BLDC motor 100 includes a movable coil assembly 106 that can linearly move on a stationary base assembly 108. The movable coil assembly 106 includes coils 110, an optional Hall-effect sensor 112 and an encoder reader 114 mounted on a movable structure 116. The stationary base assembly 108 includes linear guides 118, a magnet array 120, an encoder scale 122, limit position sensors 124 and 126, and an origin or home position sensor 128 mounted on a stationary platen or structure 130.
The linear BLDC motor 100 is connected to the BLDC amplifier 102 through a Hall-effect signal cable 132, a coil drive cable 134 and an encoder signal cable 136. The linear BLDC motor 100 is also connected to the motor controller 104 through limit sensor signal cables 138 and 140, and a home sensor signal cable 142. The BLDC amplifier 102 is connected to the motor controller 104 to exchange signals. The BLDC amplifier 102 and the motor controller 104 are both connected to a power source 144 through a power cable 146. The motor controller 104 is also connected to an external master controller/scheduler 148 to exchange communication signals.
In operation, the motor controller 104 provides control signals to the BLDC amplifier 102, while checking for signals from the limit and home sensors 124, 126 and 128. In response, the BLDC amplifier 102 sends drive signals to the coils 110 via the coil drive cable 134 to move the movable coil assembly 106 as needed. In this implementation, the BLDC amplifier 102 is configured to perform servo control based on signals from the Hall-effect sensor 112 and the encoder reader 114. Thus, the BLDC amplifier 102 functions as a digital servo amplifier. However, in other implementations, the servo control may be performed by the motor controller 104. In these implementations, the Hall-effect signal cable 132 and the encoder signal cable 136 are connected to the motor controller 104 to receive the appropriate signals for servo control.
A concern with the conventional linear BLDC motor 100 in either implementation is that the Hall-effect signal cable 132, the coil drive cable 134 and the encoder signal cable 136 are constantly flexed as the movable coil assembly 106 is linearly driven. This constant flexing can cause noise, strains and failures on these cables. Such results can cause performance degradation, errors in positioning (encoder cable failure), damages to the amplifier (coil cable failure) and dangerous run-away conditions (encoder cable failure).
Thus, there is a need for a linear BLDC motor that can reduce or eliminate the above concern.